Threonine accumulation in the seeds of a barley mutant with an altered aspartate kinase

Bright, S. W. J.; Miflin, B. J.; Rognes, Sven Erik

doi:10.1007/bf00484421

Cited by 78 publications

(46 citation statements)

References 23 publications

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“…This would be a convenient method for screening new mutants low in hordein polypeptides (38). A number of different strategies have been proposed to modify barley protein quantity and quality (6,12,34,49). The low lysine hordeins may be replaced with other storage proteins of higher lysine content (12,49), e.g.…”

Section: Discussionmentioning

confidence: 99%

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Monoclonal antibodies to hordein polypeptides

Ullrich

Rasmussen

Høyer‐Hansen

et al. 1986

Carlsberg Res. Commun.

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Monoclonal antibodies to hordein polypeptides have been produced and characterized. All antibodies reacted with more than one polypeptide, indicating that different hordein polypeptides have common epitopes. Of the seventeen isolated hybridoma lines, six secreted antibodies which reacted both with B-and C-hordein, five recognized only B-hordein and one secreted antibodies specific for C-hordein polypeptides. Two clones produced antibodies to an unidentified polypeptide doublet with an apparent molecular weight of 43 kD. These two polypeptides have at least one epitope in common with B-hordein polypeptides and are not extractable in water but in alcohol. They are not visible by Coomassie blue staining.The mutant M56 fails to synthesize B-hordein polypeptides due to a major deletion. It contains polypeptides in the B-hordein region of the gel, which have epitopes recognized by the B-hordein antibodies, but are different from B-hordeins. The 43 kD hordein doublet was more abundant in the mutant than in the wild-type endosperm, suggesting that these polypeptides like the C-hordein polypeptides are synthesized in larger amounts as a consequence of the absent B-hordein polypeptide synthesis. Mutant 1508 which has an impaired synthesis of both B-and C-hordein polypeptides was also found to be defective in the synthesis of the 43 kD polypeptide doublet. It was shown that immunofluoreseent techniques may be of practical importance to identify mutants with elevated or reduced ~tmounts of specific hordein polypeptides. Due to the higher sensitivity compared to SDS-PAGE, immunoblotting can be a useful tool for genotype identification in breeding programmes.

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Section: Discussionmentioning

confidence: 99%

“…Immunoblot assays comparing the reaction of total hordein extracts of the two genotypes with three different MAb's to hordein (lanes [3][4][5][6][7][8].…”

Section: Detection Of Hordein Polymorphism Withmentioning

confidence: 99%

Monoclonal antibodies to hordein polypeptides

Ullrich

Rasmussen

Høyer‐Hansen

et al. 1986

Carlsberg Res. Commun.

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“…4 Exp. 5 Exp. total uninhibited activity of aspartokinase should suffice for the combined flux through the aspartokinase step.…”

Section: Effects Of Aspartate-derived Amino Acids On Growthmentioning

confidence: 99%

“…Given this situation, one might expect that increased flux through aspartokinase would result in increased synthesis of threonine, but not of other aspartate-derived amino acids. Indeed, a number of plant variants selected for resistance to growth with lysine plus threonine, and containing aspartokinase activity resistant to inhibition by lysine, do show increases in soluble threonine which are large compared to any increases in the other soluble aspartate family amino acids (5,10,25).…”

Section: Regulation Of Isoleucine Biosynthesismentioning

confidence: 99%

Regulatory Structure of the Biosynthetic Pathway for the Aspartate Family of Amino Acids in Lemna paucicostata Hegelm. 6746, with Special Reference to the Role of Aspartokinase

Giovanelli¹,

Mudd²,

Datko³

1989

Plant Physiol.

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Comprehensive studies were made with Lemna paucicostata Hegelm. 6746 of the effects of combinations of lysine, methionine, and threonine on growth rates, soluble amino acid contents, aspartokinase activities, and fluxes of 4-carbon moieties from aspartate through the aspartokinase step into the amino acids of the aspartate family. These studies show that flux in vitro through the aspartokinase step is insensitive to inhibition by lysine or threonine, and confirm previous in vitro data in establishing that aspartokinase in vivo is present in two orders of magnitude excess of its requirements. No evidence of channeling of the products of the lysine-and threonine-sensitive aspartokinases was obtained, either form of the enzyme alone being more than adequate for the combined in vivo flux through the aspartokinase step. The marked insensitivity of flux through the aspartokinase step to inhibition by lysine or threonine strongly suggests that inhibition of aspartokinase by these amino acids is not normally a major factor in regulation of entry of 4-carbon units into the aspartate family of amino acids. Direct measurement of fluxes of 4-carbon units demonstrated that: (a) Lysine strongly feedback regulates its own synthesis, probably at the step catalyzed by dihydrodipicolinate synthase. (b) Threonine alone does not regulate its own synthesis in vivo, thereby confirming previous studies of the metabolism of [14C]threonine and [14CJhomoserine in Lemna. This finding excludes not only aspartokinases as an important regulatory determinant of threonine synthesis, but also two other enzymes (homoserine dehydrogenase and threonine synthase) suggested to fulfill this role. Complete inhibition of threonine synthesis was observed only in the combined presence of accumulated threonine and lysine. The physiological significance of this single example of apparent regulation of flux at the aspartokinase step, albeit under unusually stringent conditions of aspartokinase inhibition, remains to be determined. (c) lsoleucine strongly inhibits its own synthesis, probably at threonine dehydratase, without causing compensatory reduction in threonine synthesis. A fundamentally changed scheme for regulation of synthesis of the aspartate family of amino acids is presented that has important implications for improvement of the nutritional contents of these amino acids in plants.Recent in vitro studies ofaspartokinase activity (EC 2.7.2.4)

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“…For example, increasing Lys and Thr inhibits the activity of Asp kinase via a feedback inhibition loop (Clark and Lu, 2015). At high concentrations, this inhibition can lead to starvation of a downstream metabolic product, Met, which inhibits plant growth (Bright et al, 1982;Rognes et al, 1983;Heremans and Jacobs, 1995). In addition, several amino acid catabolic products, such as those emanating from branched-chain amino acids (BCAAs) or Lys degradation pathways, can be channeled toward cellular energy production under both standard and stress growth conditions (Angelovici et al, 2009(Angelovici et al, , 2011 Araújo et al, 2010;Peng et al, 2015).…”

mentioning

confidence: 99%

Network-Guided GWAS Improves Identification of Genes Affecting Free Amino Acids

et al. 2016

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Amino acids are essential for proper growth and development in plants. Amino acids serve as building blocks for proteins but also are important for responses to stress and the biosynthesis of numerous essential compounds. In seed, the pool of free amino acids (FAAs) also contributes to alternative energy, desiccation, and seed vigor; thus, manipulating FAA levels can significantly impact a seed's nutritional qualities. While genome-wide association studies (GWAS) on branched-chain amino acids have identified some regulatory genes controlling seed FAAs, the genetic regulation of FAA levels, composition, and homeostasis in seeds remains mostly unresolved. Hence, we performed GWAS on 18 FAAs from a 313-ecotype Arabidopsis (Arabidopsis thaliana) association panel. Specifically, GWAS was performed on 98 traits derived from known amino acid metabolic pathways (approach 1) and then on 92 traits generated from an unbiased correlation-based metabolic network analysis (approach 2), and the results were compared. The latter approach facilitated the discovery of additional novel metabolic interactions and singlenucleotide polymorphism-trait associations not identified by the former approach. The most prominent network-guided GWAS signal was for a histidine (His)-related trait in a region containing two genes: a cationic amino acid transporter (CAT4) and a polynucleotide phosphorylase resistant to inhibition with fosmidomycin. A reverse genetics approach confirmed CAT4 to be responsible for the natural variation of His-related traits across the association panel. Given that His is a semiessential amino acid and a potent metal chelator, CAT4 orthologs could be considered as candidate genes for seed quality biofortification in crop plants.Free amino acids (FAAs) play a pivotal role in the central metabolism of plants. FAAs serve as building blocks for protein synthesis and also are precursors for osmolytes, alternative energy, hormones, and key secondary metabolites (Rai, 2002; Araújo et al., 2010;Tzin and Galili, 2010; Angelovici et al., 2011). Studies of both developing and germinating seeds also have implicated FAAs in proper seed development and germination (Angelovici et al., 2010;Galili and Amir, 2013). Still, the genetic control of FAA metabolism in seed remains poorly understood. One reason is that FAA metabolism is tightly intertwined with essential cellular processes in plants, and manipulating FAA levels can have strong deleterious, pleiotropic effects on the entire system (Guyer et al., 1995;Galili, 2011;Ingle, 2011;Pratelli and Pilot, 2014). For example, increasing Lys and Thr inhibits the activity of Asp kinase via a feedback inhibition loop (Clark and Lu, 2015). At high concentrations, this inhibition can lead to starvation of a downstream metabolic product, Met, which inhibits plant growth (Bright et al., 1982;Rognes et al., 1983;Heremans and Jacobs, 1995). In addition, several amino acid catabolic products, such as those emanating from branched-chain amino acids (BCAAs) or Lys degradation pathways, can be chan...

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Threonine accumulation in the seeds of a barley mutant with an altered aspartate kinase

Cited by 78 publications

References 23 publications

Monoclonal antibodies to hordein polypeptides

Monoclonal antibodies to hordein polypeptides

Regulatory Structure of the Biosynthetic Pathway for the Aspartate Family of Amino Acids in Lemna paucicostata Hegelm. 6746, with Special Reference to the Role of Aspartokinase

Network-Guided GWAS Improves Identification of Genes Affecting Free Amino Acids

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